Conventionally, regarding use of an endoscope device, generally, the observation region depending on the viewing field of the endoscope inserted in a tubular structure is observed grossly or displayed on a video camera, and is recorded as still image or vide image in a recoding range specified by an observer. In this case, the observed or displayed range is limited within the observation viewing field of the endoscope, and the entire picture is recorded by repeating record of image in local range. In this method, the entire picture cannot be displayed as one seamless picture, and it lacks objectivity in identification of the position of the region of interest. Other method of continuously recording the entire image includes a video imaging method, but the entire picture cannot be displayed simultaneously, and it takes time in viewing. In the conventional methods, only two-dimensional images are recorded, and a three-dimensional structure cannot be recognized. Further, in the conventional methods, it is difficult to record objectively the hardness or motion of tissues composing a tubular structure.
For example, patent document 1 discloses an image forming system for forming continuous seamless expanded still image data inside a tubular structure of this type. This image forming system includes means for acquiring digital image data, pipe projection converting means for forming an expanded diagram in circumferential direction inside the tubular structure for each frame of the acquired digital image data, means for mosaicing, means for compressing image data, and means for compressing image data. The image forming system constructs an entire image by linking in the direction of the central axis of the tubular structure expanded diagrams in circumferential direction of each frame of the endoscopic video image.
Patent document 2 discloses a method of creating an entire image by taking images inside of a tubular structure while monitoring the posture and position information of a camera moving in the tubular structure and linking a plurality of images while matching the observation field of the camera.
Patent document 3 discloses a method of measuring the shape of the inside of a body stereoscopically by directional lighting using an endoscope with a directional scanning lighting device provided at the leading edge of the endoscope. Patent document 4 discloses a method of calculating the three-dimensional information of the subject based on interference fringes formed on the subject and distance information, using an endoscope with an interference fringe projecting unit and a laser spot projecting unit for measuring the distance provided at the leading edge of the endoscope.
Patent document 5, for example, discloses a method of detecting three-dimensional information of the subject by taking images at arbitrary time intervals while varying the amplitude of the illuminating light, and measuring the distance of each point based on the luminance of each point of the taken image and the degree of change of image gain.
Patent document 6, for example, discloses a method of creating strip-like images from 360-degree spatial video image captured using a camera moving in the tubular closure through convex mirror or fisheye lens installed in front of the camera and linking them while correcting them in the direction of camera's motion to display one entire image.
Patent document 7, for example, discloses a method of calculating the length or area of the subject by calculating the relative positions between a pipe having a single cross section and an endoscope from the endoscopic images inside the pipe observed by the endoscope moving in the pipe.
Patent document 8, for example, discloses image processing means for forming a three-dimensional model from a plurality of two-dimensional images taken while varying the optical parameters. Patent document 9 discloses a technique of forming a three-dimensional model from a plurality of images taken while changing the optical parameters. Patent document 10 discloses a technique of extracting stereoscopic information by parallax, by separating the subject observed by an endoscope with a color filter into color components.
Patent document 11, for example, discloses a technique of measuring the hardness of biological tissues by calculating reflection signals from the biological tissues with modulated ultrasonic waves emitted from an ultrasonic transducer mounted at the leading edge of an endoscope.